I'm not suggesting that fedora modifies the ABI arbitrarily just to
encourage users to switch to RHEL, but if there is there is no
expectation that 3rd party drivers that work at the beginning of a
version will work after the first update, I think that should be stated
more clearly.

There is no expectation that any software outside of Fedora repositories
can really be supported by anyone within the project. This is just
common sense. The fact that we are going to be close to upstream and not
consider proprietary kernel modules is clearly stated in the objectives
page. The front page of fedoraproject.org and overview is clear about
the focus on Free and open source software. \

The change that broke things was never pushed into the Centosplus
version I ended up using.

That is because they are just rebuilding the RHEL kernel and RHEL kernel
team does the backporting work to remain on pretty much the same kernel.
Again Fedora does have that kind of resources nor does match the goal of
Fedora. If you want and prefer RHEL or rebuilds just continue using that
instead.

If fedora must send every new and untested

change on to the users, how about some easier way to avoid them if they
break your hardware, like making kernel updates opt-in within a release
version?

Fedora is targeted towards the end users who prefer running close to the
latest versions. These are not untested nor is every version in all
packages pushed into the stable branches. All updates are opt-in anyway.
So if the older version works for you, you don't have to update.